It was found that Tester.java did not work for hw5.
As was previous problem, it is caused by the slight incompatibilities
of different versions of Java SDKs.

Specifically, if you follow exactly the procedures to run the skeleton 
program given in the description of this assignment, at the 
5th step when running Sink program, youmay see the followinng 
output:
Local Socket Port: xxxx
Tester is not bound in registry
Source offerer is not found at remote registry
......

The above output shows that Naming.lookup("Tester") in SinkTester.java 
failed when lookup the class Tester. 

To solve this problem, we can take the following two steps (Step 1 is used 
for debugging, and you can skip it):

1. add code to print exception messages for Naming.lookup().
Add the following lines of code:

System.out.println("Naming.lookup() err: " + e.getMessage());
e.printStackTrace();

at Line 83 of SinkTester.java and Line 105 of SourceTester.java.
Therefore, we are able to see the detailed exception messages. By 
following the execution procedures available in the description for this 
assignment, we can observe the following output:

Local Socket Port: 1025
Tester is not bound in registry
Naming.Lookup() err: error unmarshalling return; nested exception 
is: 
java.lang.ClassNotFoundException: Tester_Stub
java.rmi.UnmarshalException: error unmarshalling return; nested exception 
is: 
java.lang.ClassNotFoundException: Tester_Stub
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at java.rmi.Naming.lookup(Naming.java:84)
at SinkTester.main(SinkTester.java:77)
......

This means that Tester_Stub.class, which is generated by the RMI compiler 
(when running "rmic Tester" in the first step), can not be located by 
SinkTester. RMI server is supposed to send the class files to the client 
(i.e., SinkTester), however, the class file (Tester_Stub.class) is not 
sent by the RMI server in this case.

2. We can take the following quick fixes to make the clients (both 
SinkTester and SourceTester) be able to retrieve the needed class file 
Tester_Stub.class:

(a) copy the class files (Tester/*.class) to Sink/ and Source/

(b) set CLASSPATH environment variable for Sink and Source to guide the 
location of class files. For example,

$ export CLASSPATH=$CLASSPATH:~/cs555/hw5/Tester:~/cs555/hw5/Sink:~/cs555/hw5/Source

given that your programs are located in ~/cs555/hw5/.

Note that there are other fixes which can be more complicated, which can 
be found in the documents of RMI and archives of Sun's RMI mailing list.